The Stovebolt Site Forums The Shop Area Engine Shop 3/4-ton rear end

My '53 3/4-ton has the original rear end which I believe is a 4.57. I'm told an upgrade to a 4.11 would be a good idea for highway travel. Could someone who has made this change walk me through step by step please? I have the shop manual and see that pulling the axles is only a matter of removing the 8 bolts on each side (I think a 1/2 ton is a different setup) and then sliding them out. I will try to find a 4.11 at a junk yard, but what all will I need in order to do the bare minimum replacement and still keep my pumkin, etc? What about any special tools or tricks of the trade to make this as easy as possible? I already have the drive line off due to restoration and have changed the pinion seal. Do I just unbolt the front of the carrier or does the pinion nut also have to come off? Once inside, what needs to be done? Any step by step help would be greatly appreciated and I see by some posts that others may also benefit from your expertise and wisdom.

I just dropped a 4.11 set into my 55 1st series. It helped that I have the truck completely apart to do the swap. First step is to drain the oil from the rear end. Not sure the right way to do it, but if you just take the rear cover off the diff, the oil will pour out! Make sure to have a good sized oil pan for that 90 weight as there are 3 quarts of oil in that rear end. After that, you can pull the axles by just removing the eight bolts and sliding them out. No need to take them all the way out, just enough to release them from the gearset. Next you go ahead and remove the 10? bolts that hold the pumpkin in place. Be careful, the pumpkin weighs a ton and will hurt if dropped.

After you have it removed it is simply a matter of putting the 4.11 pumpkin in place, replacing the bolts, axles and rear cover and filling with oil. It really is that simple

The gasket you need for the rear cover and pumpkin can be found at NAPA (part # P39130).

Keep in mind this is for a 55 first series. I think the 3/4 tons are the same for rear ends but maybe someone else can verify that this will work for your 53 as well.

Good luck.

Rick, The Kook and I did the swap on his '51 GMC in my garage. He took a few pics and posted them on his web page.

Here is the link

It was a straight forward job. If you have any other questions , ask away.

Hi Steve. Thanks for the response. When you remove the bolts that hold the pumkin in place, does the ring gear and pinion gear come out with it? Just pull the whole thing out and slide the new one in? What about adjustments? Sounds pretty easy. Do you need to back off the adjustment for the backlash before taking it apart?

When you remove those bolts, watch out. That pumpkin is coming out at you..

No need to back off anything before you pull the chuck. Keep it simple, you won't have any trouble..

You should make sure the splines on your axle are the same as the side gears in the new diff. This is one of the easiest things there is to swap, do just like the other guys have been telling you.

Yes, just the bolts that hold the pumpkin to the housing.There are ten.
When you have it out, clean out the housing as much as you can.You might want to pull the outer hubs and clean & inspect the bearings.You will want to have good clean oil all throughout the rear-end.
Be sure to squrt some oil on all bearings and gears before re-assembly so nothing will start out dry metal to metal.
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Oh yes,,, It is really heavy.If you happen to have a bigger floor jack or stack some wood planks just under the pumpkin so you can set it on that as it comes out.You will find out how heavy it is when you go and get one from a wrecking yard or friend.

It really is as simple as everyone has stated. Replace the whole pumkin and then you will likely have no adjustment. When looking for a new set look at 67-72 3/4 ton with auto trans as they almost all had the 4:11 that will bolt right in.

Thanks for all the good info gents. I'll let you know how things go.

The OldKarKook web page on this subject is great. A real classic.

Is it a 4.11 (37/9 teeth) or a 4.10 (41/10 teeth) or did GM make both for the 67-72 3/4-ton?

It is a 41/10.. 4.10

Rick,

Sorry it took me so long to reply, but you seem to have gotten the answers from the rest of the forum! Good stuff here. I got all my info from them. As well, the ring/pinion is 41/10 as mentioned earlier. Mine had the 41 teeth on the ring gear to confirm.

Remember, the pumpkin is heavy since it includes everything out of the middle. Again, watch the toes and fingers. It could easily take some off if you drop it. A floor jack could make this easier/safer to do.

Good luck and be careful.